When House Majority Leader Eric Cantor walked out of the debt-ceiling negotiations last week in a hissy fit, he once more dramatized the simple truth that cannot speak its name. This Republican Party is addled by an extremist ideology and cankered by a vengeful partisanship. In a time of national crisis, it is locked into ideological litmus tests — no new taxes — and opposed to anything the “Kenyan, socialist” president might propose.

This makes the routine difficult and the necessary impossible. Republicans threaten to blow up the world economy by refusing to lift the debt limit without getting drastic cuts in the deficit. Puffed up with locker-room bravado, they set a high bar — more than $2 trillion in deficit reduction over 10 years, a dollar or more for every dollar hike of the debt limit.

But Cantor detonates the talks because, in fact, Republicans won’t negotiate on how to reach their goal. They will accept no new taxes, no closing of tax loopholes, no crackdown on overseas tax havens. The richest 400 Americans enjoy a lower tax rate than their cleaning women, but their taxes cannot be raised. The biggest corporations, such as General Electric, pay little or no taxes on billions in profits, yet their loopholes cannot be closed.

So the entire $2 trillion must come from spending cuts. But Republicans also won’t agree to mandated cuts in defense spending, despite the fact that the defense budget has soared since Sept. 11, two unfunded wars contributed trillions to the debt, and the Pentagon is one of the nation’s leading sources of waste, fraud and abuse. Some tea party members suggest that defense spending is on the table, but the negotiators oppose any separate cap for defense spending, leaving the issue in the hands of the very appropriators who have regularly insisted on spending more than the Pentagon asks for.

Republicans are so strait-jacketed by their “pledge” never to raise any taxes that any Republican suggesting the closing of subsidies to big oil or ethanol makers? is considered a profile in courage. And now, the conservative arch-druid Sen. Jim DeMint adds a new litmus test for any presidential candidate: He or she must not only embrace the no-tax pledge but promise to pass a constitutional amendment to balance the budget. This inanity left over from Newt Gingrich’s 1994 “Contract With America” will now be a feature of Republican presidential debates.